A basic advantage for an all-plastic PAR lamp is its light weight as compared to the glass construction now in use. Consequently, a minimal wall thickness for said plastic PAR lamp construction is desirable to provide as little weight as possible while still recognizing that either mechanical and heat distortion of the plastic material both during lamp assembly and thereafter in use can give rise to a number of serious problems. Such a problem is experienced during assembly of an all plastic
lamp for an automotive headlamp construction where a reliable leak-proof seal is desired when the plastic lens member is joined to the reflector. Any mechanical or head distortion at the sealing rim of said reflector member can preclude a reliable seal from being formed when either ultrasonic or vibration of welding techniques are used to provide the joinder. Subsequent heat distortion in the sealing rim region of the assembled construction during lamp operation at elevated temperatures can cause much the same problem in maintaining a leak-proof seal between the assembled members. Consequently, a more reliable sealing means for an all-plastic PAR lamp construction is desired which maintains the leak-proof seal both during lamp assembly as well as during subsequent lamp operation.